Axi-nozzle ejector seal

ABSTRACT

A nozzle for a gas turbine engine is provided which includes an outer casing, a convergent section, a divergent section, an external fairing, and a collapsible seal member. The divergent section has an aft end and a forward end, and the forward end of the divergent section is pivotally attached to the convergent section. The external fairing has an aft end and a forward end. The forward end of the external fairing is pivotally attached to the outer casing and the aft end of the external fairing is pivotally attached to the aft end of the divergent section. The external fairing is disposed radially outside of the divergent section. The collapsible seal member extends between the outer casing and the divergent section, circumferentially around and outside of the divergent section.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to gas turbine engines havingconvergent/divergent nozzles in general, and apparatus for sealingwithin nozzles in particular.

2. Background Information

An exhaust nozzle provides a means for optimizing thrust produced withina gas turbine engine. In augmented gas turbine engines,convergent/divergent (CID) nozzles are particularly favored because ofthe multitude of nozzle positions possible. Flaps circumferentiallydistributed aft of the augmentor form the convergent and divergentsections for which the nozzle is named. Flap seals disposed betweenadjacent flaps minimize gas leakage between flaps in both sections. Theconvergent section is pivotally connected to the augmentor and to thedivergent section. The divergent section is pivotally connected to theconvergent section and to an external fairing positioned radiallyoutside of the divergent section. The opposite end of the externalfairing is pivotally attached to a static outer casing which surrounds aportion of the nozzle. Together, the outer casing, the convergent anddivergent sections, and the external fairing form a plenum hereinafterreferred to as the “nozzle plenum”.

Because of the high temperature of the core gas exiting the turbine andaugmentor, nozzles are cooled with air bled off of the fan at a lowertemperature and a higher pressure than that of the core gas flow passingthrough the nozzle. Cooling air enters the core gas path within theaugmentor via cooling holes in the augmentor liner and subsequentlypasses into the nozzle as a layer of cooling air traveling along thesurface of the nozzle flaps and flap seals. Cooling air within thenozzle plenum cools the opposite side of the flaps and flap seals.

One significant disadvantage of this approach is that the layer ofcooling air traveling along the augmentor liner and nozzle increases intemperature as a function of distance traveled. At the same time thetemperature increases, the geometry of the layer erodes and furtherinhibits the ability of the cooling air layer to thermally protect theadjacent augmentor or nozzle component. As a result, adequate coolingair flow for the convergent section may be insufficient for thedivergent section. If the cooling air flow is increased to meet theminimum required for the divergent section, an excessive amount would beused to cool the convergent section. A person of skill in the art willrecognize that it is a distinct advantage to minimize the amount of bledcooling air used within a gas turbine engine.

To avoid the above described problems, some applications employ coolingair ejectors disposed in the divergent flaps and flap seals. Cooling airfrom the nozzle plenum passes through the ejectors and either forms anew layer, or augments an existing layer, traveling aft over thedivergent flaps and flap seals. This approach improves the cooling layerperformance along the divergent section. A problem with this approach,however, is that the cooling air initially produced as fan bypass airencounters numerous pressure drops within the bypass air plenum as ittravels aft from the fan to the nozzle. One of the more significantdrops occurs in the nozzle plenum, where the cooling air is directedtoward the joint between the divergent section and the external fairing.

What is needed is a nozzle that provides adequate cooling for both theconvergent and divergent sections and one that uses minimal cooling air.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide a nozzlethat requires minimal cooling air.

It is another object of the present invention to provide a nozzle thatadequately cools the divergent flaps and flap seals.

It is still another object of the present invention to provide a sealingapparatus for a nozzle that is effective for multiple nozzle positions.

It is still another object of the present invention to provide a sealingapparatus that is easily manufactured and implemented.

According to the present invention, a nozzle for a gas turbine engine isprovided which includes an outer casing, a convergent section, adivergent section, an external fairing, and a collapsible seal member.The divergent section has an aft end and a forward end, and the forwardend of the divergent section is pivotally attached to the convergentsection. The external fairing has an aft end and a forward end. Theforward end of the external fairing is pivotally attached to the outercasing and the aft end of the external fairing is pivotally attached tothe aft end of the divergent section. The external fairing is disposedradially outside of the divergent section. The collapsible seal memberextends between the outer casing and the divergent section,circumferentially around and outside of the divergent section.

According to one aspect of the present invention, the divergent sectionincludes a plurality of ejector slots through which cooling air maypass. The ejector slots are oriented such that cooling air may pass fromthe nozzle plenum, through the divergent section, and travel along thesurface of the flap as a layer before mixing with the passing core gasflow.

An advantage of the present invention is that it minimizes the volume ofcooling air necessary to adequately cool the divergent section of thenozzle. A person of skill in the art will recognize that nozzles havingflaps and flap seals are notorious for cooling air leakage. The presentinvention nozzle, which includes the collapsible seal, limits coolingair leakage within the nozzle plenum, and thereby minimizes the totalvolume of cooling air necessary. The present invention also minimizesthe cooling air volume requirement by enabling the divergent section tobe cooled more efficiently. The embodiment using the collapsible seal incombination with the ejector slots in the divergent section avoidshaving to provide excessive cooling in the convergent section to insureadequate cooling in the divergent section.

Another advantage of the present invention is that it minimizes theamount of work required to provide cooling air to ejector openingsdisposed in the divergent section. The collapsible seal portion of thepresent invention minimizes cooling air pressure losses between the fanand the divergent section thereby minimizing the amount of work requiredto provide the cooling air. A person of skill in the art will recognizethat work required to increase the pressure of the cooling air does notadd to the thrust of the engine and therefore decreases the efficiencyof the engine.

These and other objects, features and advantages of the presentinvention will become apparent in light of the detailed description ofthe best mode embodiment thereof, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic partial view of a gas turbine engine augmentorand nozzle.

FIG. 2 is a diagrammatic partial view of the collapsible seal of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 and 2, a nozzle 10 for a gas turbine engine isshown having an outer casing 12, a divergent section 14, a convergentsection 16, an exterior fairing 18, and a collapsible seal 20. Anaugmentor 22 is partially shown forward of the nozzle 10 contiguous withthe convergent section 16. The convergent section 16 of the nozzle 10 isforward of the divergent section 14 and the intersection between the twosections 14,16 forms the throat of the convergent/divergent nozzle 10.The outer casing 12 is a static structure that surrounds the augmentor22 and a portion of the nozzle 10. The annular region 24 bounded by theconvergent section 16, the divergent section 14, and the externalfairing 18 is referred to as the nozzle plenum 24.

The convergent section 16 of the nozzle 10 includes a plurality ofconvergent flaps 26 and convergent flap seals (not shown)circumferentially distributed aft of the augmentor 22. The convergentsection 16 is attached to pivotable linkages 28 which are attached tobrackets 30 mounted on the outer casing 12. The pivot point 32 of eachlinkage 28 is adjacent the intersection between the augmentor liner 34and the convergent section 16. The position of the linkage pivot points32 enables the convergent section 16 to pivot relative to the augmentorliner 34 as though it was pivotally attached to the augmentor liner 34.The divergent section 14 includes a plurality of divergent flaps 36 anddivergent flap seals 38 circumferentially distributed aft of theconvergent section 16. The divergent section 14 is pivotally attached tothe linkages 28 supporting the convergent section 16. The opposite endof the divergent section 14 is pivotally attached to the exteriorfairing 18. In one embodiment, each divergent flap 36 and flap seal 38includes a cooling air passage 40 usually in the form of a slot,commonly referred to as an “ejector slot” 40. The exterior fairing 18includes a plurality of exterior flaps 42 and exterior flap seals (notshown) arranged in a manner similar to that of the divergent sectionflaps 36 and flap seals 38. The aft end of the exterior fairing 18 ispivotally attached to the divergent section 14. The forward end of theexterior fairing 18 is pivotally attached to the outer casing 12.

The collapsible seal 20 includes an outer case mounting flange 44, adivergent section mounting flange 46, and a collapsible member 48extending therebetween (see FIG. 2). The collapsible member 48 consistsessentially of a pliable material that collapses sufficiently incompression to accommodate nozzle movement. The term “collapsible” isused to describe the member's ability to fold or to bend to accommodateall possible nozzle 10 positions and configurations. In one embodiment,the collapsibility of the member 48 is augmented with mechanicalfeatures 52 that improve the member's ability to fold or bend. Pleats orcorrugations are examples of mechanical features 52 that may be used toaugment the collapsibility of the member 48. A plurality of meteringorifices 50 are disposed in the collapsible seal 20 to permit thepassage of cooling air through the seal 20. Alternatively, meteringorifices could be formed between outer case structure 12 and the outercase mounting flange 44, or between the divergent section 14 and thedivergent section mounting flange 46. In a preferred embodiment, thecollapsible member 48 includes a fabric made from aramid or similar typefibers. A fabric made from Kevlar™, an E. I. DuPont Company product, isan acceptable aramid type fabric. In the most preferred embodiment, thearamid fabric is impregnated with a RTV (room temperature vulcanizing)type silicon-rubber composite product. The RTV silicon product providesa sealing function. That impedes the flow of core gas through thefabric.

Referring to FIG. 1, in the operation of the engine cooling air at alower temperature and higher pressure than the core gas flow is bled offof the fan and passed into the annulus 54 formed between the augmentorliner 34 and the outer casing 12. A percentage of the cooling air bleedsout of the annulus 54 through the apertures 56 in the augmentor liner 34and forms a layer 58 of cooling air traveling aft along the augmentorliner 34. The layer 58 continues aft passing over the convergent section16, transferring heat away from the convergent section 16 along the way.The cooling air that does not enter the augmentor 22 continues aft intothe nozzle plenum 24. The collapsible seal 20 divides the nozzle plenum24 into a forward region 60 and an aft region 62. The cooling air firstenters the forward region 60 and is inhibited from moving into the aftregion 62 by the collapsible seal 20, except through the meteringorifices 50 (see FIG. 2) disposed within (or adjacent) the collapsibleseal 20. The advantage here is that only that volume of cooling air thatis necessary to cool the aft region 62 is allowed to enter the aftregion 62. Consequently, the volume of cooling air used is minimized.

In the embodiment which includes ejector slots 40 disposed within thedivergent section, cooling air passes from the forward region 60 throughthe ejector slots 40 to augment an existing cooling air layer, or toestablish a new cooling air layer, aft of the slot along the surface ofthe divergent flap 36 or flap seal 38. The advantage of using thecollapsible seal 20 in this embodiment is two-fold. First, thecollapsible seal 20 minimizes cooling air use as described above.Second, the collapsible seal 20 minimizes pressure losses for thatcooling air which enters the nozzle 10 via the ejector slots 40.

Although this invention has been shown and described with respect to thedetailed embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and the scope of the invention.

We claim:
 1. A nozzle for a gas turbine engine, said nozzle comprising:an outer casing; a convergent section; a divergent section, having anaft end and a forward end, said forward end pivotally attached to saidconvergent section; an external fairing, having an aft end and a forwardend, said forward end pivotally attached to said outer casing and saidaft end pivotally attached to said aft end of said divergent section,wherein said external fairing is disposed radially outside of saiddivergent section; and a collapsible seal, extending between andconnected to said outer casing and said divergent section,circumferentially around and outside of said divergent section, whereinsaid seal is collapsible to accommodate movement of the nozzle.
 2. Anozzle for a gas turbine engine according to claim 1, wherein saidcollapsible seal includes a collapsible member with aramid fibers.
 3. Anozzle for a gas turbine engine according to claim 2, wherein saidcollapsible member is impregnated with RTV silicon-rubber composite. 4.A nozzle for a gas turbine engine according to claim 1, wherein saiddivergent section comprises a plurality of ejector slots.
 5. A nozzlefor a gas turbine engine according to claim 4, wherein said collapsibleseal attaches to said divergent section aft of said ejector slots.
 6. Anozzle for a gas turbine engine according to claim 5, wherein saidcollapsible seal includes a collapsible member with aramid fibers.
 7. Anozzle for a gas turbine engine according to claim 6, wherein saidcollapsible member is impregnated with RTV silicon-rubber composite. 8.A collapsible seal for use in a gas turbine engine nozzle, between theouter casing of the engine and a divergent section of the nozzle, saidcollapsible seal comprising: a first mounting flange for connection tothe outer casing of the engine; a second mounting flange for connectionto the divergent section of the nozzle; and a collapsible member,extending between said first and second mounting flanges, wherein saidseal is collapsible to accommodate movement of the nozzle.
 9. Acollapsible seal according to claim 8, wherein said collapsible membercomprises aramid fibers.
 10. A collapsible seal according to claim 9,wherein said collapsible member is impregnated with RTV silicon-rubbercomposite.